Conventionally, there has been known a method of manufacturing a semiconductor device which includes an oxide film removing step where an oxide film formed on a surface of a semiconductor substrate is partially removed (for example, see patent literature 1).
As shown in FIG. 9A to FIG. 9C, the conventional method of manufacturing a semiconductor device includes, in the following order: a semiconductor substrate preparing step (not shown in the drawing) where a semiconductor substrate 910 having a pn junction parallel to a main surface thereof and having the main surface thereof covered by an oxide film 916 is prepared; a trench forming step (see FIG. 9A) where a pn junction exposure portion is formed in the inside of a trench 920 by forming the trench 920 having a depth exceeding the pn junction from one main surface of the semiconductor substrate 910; a glass layer forming step (see FIG. 9B) where a glass layer 922 is formed so as to cover the pn junction exposure portion in the inside of the trench 920; a photoresist layer forming step (see FIG. 9C) where a photoresist layer 924 (made of an organic resist) is formed so as to cover the glass layer 922; an oxide film removing step (see FIG. 9D) where the oxide film 916 formed on the surface of the semiconductor substrate 910 is partially removed by etching using the photoresist layer 924 as a mask; a photoresist layer removing step (not showing the drawing) where the photoresist layer 924 is removed; and an electrode forming step (see FIG. 9E) where an electrode 934 is formed on a portion 930 where an electrode is to be formed.
According to the conventional method of manufacturing a semiconductor device, a glass layer 922 for passivation is formed in the inside of the trench 920 and, thereafter, the semiconductor substrate is cut thus manufacturing a highly reliable mesa-type semiconductor device.